The present invention is directed to a rod seal for sealing an actuating rod to a housing wall through which the rod passes in applications where the rod must be capable of movement relative to the housing in two or more mutually perpendicular directions.
A primary example of a rod seal having the foregoing requirements is that of the choke actuating rod of a carburetor for an internal combustion engine. The carburetor body is formed at its upper end with an annular radially outwardly projecting flange which surrounds the induction air passages which open at the top of the carburetor body. The upper surface of this annular flange serves as an annular seat for the air cleaner which filters dirt particles from outside air drawn into the induction air passages by the manifold vacuum during operation of the engine. When the air cleaner is mounted upon the annular flange, it defines a closed chamber at the top of the carburetor body whose only inlet is through the filter of the air cleaner. A choke plate is mounted within this chamber at the inlet of one or more of the induction air passages for pivotal movement in a well known manner to adjustably control the flow of air into the passages to provide an enriched fuel mixture to the engine during cold start and warm up. The rotatable shaft of the choke plate is normally located above the annular sealing flange and provided with a crank arm at one end which is coupled to one end of the choke actuating rod, the other end of the rod being coupled to an automatic choke mechanism mounted on the exterior of the carburetor body. Because the choke plate carrying shaft is located above the annular sealing flange which supports the air cleaner, the choke rod-crank shaft connection must be located within the closed clean air chamber established by the air cleaner when mounted on the carburetor. A hole must be provided through the annular flange to permit the actuating rod to pass through the flange from the externally mounted actuating member into the clean air chamber. While the main component of motion of the rod in actuating movement is longitudinally of the rod, the rod must also move laterally because of the circular path of the end of the crank arm to which it is connected within the chamber. This requires the hole through the flange to be substantially larger than the rod, and this enlarged opening provides a substantially unrestricted flow path for the flow of uncleaned outside air into the clean air chamber induced by the sub atmospheric (manifold vacuum) pressure within the clean air chamber.
The conventional arrangement for sealing this opening is only partially effective. A generally rectangular slider plate of dimensions larger than the hole in the annular sealing flange is mounted for sliding movement in substantial engagement with the external surface of the sealing flange through which the rod projects. The slider plate is formed with an opening through which the actuating rod extends. This arrangement only partially seals the opening because the opening through the slider plate must be substantially larger than the diameter of the rod to accommodate insertion of a key like "dog ear" formed at the end of the actuating rod which passes through a key hole shaped opening in the choke plate crank to retain the actuating rod coupled to the crank. This enlarged opening in the plate and the clearance between the slider plate and sealing flange provide two paths for the flow of unclean outside air to the clean air chamber. While that path between the slider plate and sealing flange surface can be minimized by minimizing the clearance between these two members, in order to provide for insertion of the "dog ear" key on the rod through the bore in the slider plate, the diameter of this bore must be at least twice that of the rod diameter.
The present invention is directed to a seal which eliminates this latter problem.